All things being equal, Col. Anthony Henderson has the military background that the Marine Corps says it prizes in a general: multiple combat tours, leadership experience and the respect of those he commanded and most who commanded him.

Yet three times he has been passed over for brigadier general, a prominent one-star rank that would put Colonel Henderson on the path to the top tier of Marine Corps leadership. Last year, the Navy secretary, Richard V. Spencer, even added a handwritten recommendation to Colonel Henderson’s candidacy: “Eminently qualified Marine we need now as BG,” he wrote.

But never in its history has the Marine Corps had anyone other than a white man in a senior leadership post. Colonel Henderson is Black.

“Tony Henderson has done everything you could do in the Marines except get a hand salute from Jesus Christ himself,” said Milton D. Whitfield Sr., a former Marine gunnery sergeant who served for 21 years.

Proud and fierce in their identity, the Marines have a singular race problem that critics say is rooted in decades of resistance to change. As the nation reels this summer from protests challenging centuries-long perceptions of race, the Marines — who have long cultivated a reputation as the United States’ strongest fighting force — remain an institution where a handful of white men rule over 185,000 white, African-American, Hispanic and Asian men and women.

“It took an act of Congress last year to get them to integrate by gender at the platoon level,” said Representative Anthony G. Brown, Democrat of Maryland and a former Army helicopter pilot. “And now they continue to hold onto that 1950s vision of who Marines are.”

Current and former Marine Corps officials point to Colonel Henderson’s personality as an explanation for why he has been passed over, including what they call his tendency to speak his mind — traits that have not disqualified white Marine colonels.

Since the Marines first admitted African-American troops in 1942, the last military service to do so, only 25 have obtained the rank of general in any form. Not one has made it to the top four-star rank, an honor the Marines have bestowed on 72 white men. Six African-Americans reached lieutenant general, or three stars. The rest have received one or two stars, the majority in areas like logistics, aviation and transport, areas from which the Marine Corps does not choose its senior leadership.